In the past, refrigeration apparatuses have been known which are provided with a refrigerant circuit through which refrigerant is circulated to thereby perform a refrigeration cycle. This type of refrigeration apparatus finds wide utility in the field of air conditioners or the like.
For example, JP-A-2001-107881 (hereinafter referred to as the patent document) shows a refrigeration apparatus in which a positive displacement fluid machine is connected in the refrigerant circuit. This fluid machine is configured by mechanically connecting together an expander and a compressor via a rotation shaft. In addition, an indoor heat exchanger and an outdoor heat exchanger are connected in the refrigerant circuit.
In the refrigeration apparatus, the refrigerant in the refrigerant circuit is circulated to thereby perform a refrigeration cycle, whereby cooling or heating of the room is accomplished. More specifically, for example, during the heating operation, the refrigerant which has been compressed in the compressor of the fluid machine flows through the indoor heat exchanger. In the indoor heat exchanger, the refrigerant gives up heat to the indoor air. As a result, heating of the room is accomplished. The refrigerant which has given up heat in the indoor heat exchanger flows into the expander of the fluid machine. The refrigerant expands in the expander, wherein internal energy produced upon expansion of the refrigerant in the expander is converted through the rotation shaft into power to rotationally drive the compressor. The refrigerant which has expanded in the expander then flows through the outdoor heat exchanger. In the outdoor heat exchanger, the refrigerant extracts heat from the outdoor air and is evaporated.
As described above, in the refrigeration apparatus of the patent document, internal energy produced upon expansion of the refrigerant in the expander is utilized as power to drive the compressor. The refrigeration apparatus of the patent document tries to realize a refrigeration cycle having a high energy efficiency (i.e., a refrigeration cycle at a high COP) by reduction in the power load of the compressor.